Santiago Romero wrote:
> 
>> Hi,
>>
>> Quoting the documentation[1]:
>>
>> "The unverified_recipient_defer_code parameter (default 450) specifies
>> the numerical Postfix SMTP server reply code when a recipient address
>> probe fails with some temporary error. Some sites insist on changing
>> this into 250. NOTE: This change turns MX servers into backscatter
>> sources when the load is high."
>>
>>   
> 
> So, do you mean that changing this parameter to 250 would make postfix
> to accept the email?
> 

Hi,

No. You should leave this parameter in its default value.

I realize now that I shouldn't have quoted the entire piece from the
documentation, only the relevant part. You're not the only one who
misinterpreted my post. Sorry for that.

I only wanted to quote this:

"The unverified_recipient_defer_code parameter (default 450) specifies
the numerical Postfix SMTP server reply code when a recipient address
probe fails with some temporary error."

This is the relevant part, and answers the question you had. Everything
else is irrelevant - and as Brian Evans ponted out earlier (and the
documentation too), setting this parameter to 250 will generate bounces
and backscatter. And that is very bad!

Using "reject_unverified_recipient" should produce the behaviour you are
asking for. I also set "unverified_recipient_reject_code = 550". This
makes postfix permanently reject when the recipient address is confirmed
 not existing.

When postfix does not know it'll reject the connection with a 450 (or
whatever unverified_recipient_defer_code is set to), which should be
fine for most cases.

When the address is confirmed to exist, everything is cool and mail is
accepted.

Maybe I should add that I use Postfix v2.6.2 just in case there are
differences in default values between versions.

HTH,
Mikael

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